Gastruloid

Gastruloids are three dimensional aggregates of embryonic stem cells (ESCs) that, when cultured in specific conditions, exhibit an organization resembling that of an embryo.

[4] In this work, the EBs were able to organise themselves into structures with polarised gene expression, axial elongation/organisation and up-regulation of posterior mesodermal markers.

This was in stark contrast to work using EBs from mouse ESCs, which had shown some polarisation of gene expression in a small number of cases but no further development of the multicellular system.

[5][6] Following this study, the Martinez Arias laboratory in the Department of Genetics at the University of Cambridge demonstrated how aggregates of mouse embryonic stem cells (ESCs) were able to generate structures that exhibited collective behaviours with striking similarity to those during early development such as symmetry-breaking (in terms of gene expression), axial elongation and germ-layer specification.

However, changes in the culture conditions can elicit morphogenesis, most significantly gastruloids have been shown to form somites[13][12] and early cardiac structures.

An example of a Gastruloid formed from Brachyury::GFP mouse ESCs, treated with a pulse of the Wnt/β-Catenin agonist CHIR99021 between 48 and 72h and imaged by wide-field fluorescence microscopy at 120h. Notice the polarised expression of Brachyury::GFP (Bra) at the elongating tip of the Gastruloid. Image from van den Brink et al. (2014), used with CC-BY licence.